Cynthia E. Wagner, MD, and Gorav Ailawadi, MD
Concept
- Indications and outcomes for reoperative mitral valve surgery
- Considerations for re-repair vs. primary replacement
- Considerations for bioprosthetic vs. mechanical valve replacement
- Operative details specific to redo mitral valve surgery
- Complications of mitral valve surgery
Chief complaint
“A 70-year-old woman with a 3-month history of dyspnea on exertion is referred by her cardiologist after a TTE showed severe MR due to leaflet prolapse, mitral annular calcification, mild pulmonary hypertension, and LVEF 55%. The patient underwent mitral valve repair for leaflet prolapse ten years ago.”
Differential
The diagnosis has been established and should be confirmed with a detailed H&P and appropriate tests. In the absence of an echo report, the differential diagnosis for these symptoms in a patient s/p valve repair would include recurrent MR, MS, AS, AI, cardiomyopathy, CHF, pulmonary hypertension, stable/unstable angina, or primary pulmonary disease.
History and physical
A thorough history to establish functional status, assess for comorbidities (HTN, HLD, DM, AF, CAD, carotid disease, PVD, CKD), and determine all prior surgeries or procedures. Detailed operative reports from all prior cardiac surgeries should be obtained. Some patients will not recognize stent placement (cardiac or aortoiliac) or pacemaker placement as surgery and should be asked directly about these procedures, as they will guide further work-up and may impact plans for cannulation. A history of trauma to the right chest should be inquired about if a right lateral thoracotomy is planned. Medications should be reviewed and indications for anticoagulation should be questioned, as this may impact choice of valve prosthesis if mitral valve replacement (MVR) is planned. Social factors, including family planning in younger female patients, occupation, and hobbies, should be identified that may increase bleeding risk from anticoagulation for a mechanical valve. All patients should be asked about prior stroke and residual deficits prior to cardiac surgery. A focused physical examination should follow, assessing for heart rate and rhythm, murmurs, bruits, bibasilar rales, and lower extremity edema, and noting all prior surgical incisions. In select patients, assess fall risk and frailty with grip strength and 15 ft walk test.
Tests
- EKG to assess for AF.
- CXR to assess number of sternal wires, may show cardiomegaly and cephalization of pulmonary blood flow.
- Non-contrast chest CT to assess distance between posterior sternum and anterior RV as well as extent of aortic calcification and mitral annular calcification, and CTA chest to identify course of patent grafts if patient has undergone prior CABG.
- CTA abdomen/pelvis to assess vessel caliber and tortuosity if femoral cannulation is planned.
- Preoperative TEE to better visualize mitral valve pathology is essential in determining mechanism of MR, especially if re-repair is planned, and may identify thrombus in the LA appendage if patient has AF.
- Cardiac catheterization should be routine, as undiagnosed CAD may result in perioperative morbidity or the need for further reoperation and is essential in determining patency of grafts in patients who have undergone prior CABG.
- Consider right heart catheterization in patients with severe LV or RV dysfunction or symptomatic patients in class III-IV CHF.
- Carotid duplex in high-risk patients.
- PFTs in select patients.
- Obtain prior operative report to include year of surgery, details of operation, valve exposure, possible location of grafts, manufacturer of valve.
Index scenario (additional information)
“The patient has had progressively worsening MR and LV function on annual TTE and has been asymptomatic on a diuretic and an ACE inhibitor until recently. She does not have AF and does not require anticoagulation for any pre-existing disease. She has HTN, hyperlipidemia (HLD), and DM, and a preoperative cardiac catheterization shows severe multi-vessel CAD. This prompts a carotid duplex prior to cardiac surgery. A chest CT shows a mildly dilated RV immediately posterior to the sternum and an ascending aorta with minimal atherosclerotic disease. A CTA abdomen/pelvis is done in anticipation of femoral cannulation prior to redo sternotomy.”
Treatment/management
This patient meets criteria for a reoperative mitral valve surgery according to current ACC/AHA guidelines.
Table 40-1. Indications for intervention in mitral valve disease.
| Symptomatic patients with moderately severe to severe MR (3-4+) or moderate to severe MS Asymptomatic patients with severe MR with any of the following conditions: LVEF < 60% LV end-systolic diameter > 40-45 mm PHTN with PASP > 50-60 mmHg New-onset AF |
Mitral valve repair eliminates the risks associated with MVR, including bleeding, thromboembolic events, and prosthetic valve endocarditis. Re-repair is associated with lower mortality compared to replacement at reoperation and may be attempted on previously repaired mitral valves unless severe calcification of the leaflets, annulus, and subvalvular apparatus or extensive leaflet destruction from endocarditis is present. However, this requires a high comfort level with redo repair strategies – it is never wrong to replace especially during a redo. Etiology of valve disease dictates durability of repair. After primary mitral valve repair, freedom from reoperation at 10 years is 95% in patients with degenerative valve disease vs. 53% in patients with rheumatic valve disease. Early failure after repair (< 2 years) is often the result of technical failure, while late failure after repair (> 2 years) is often due to progression of native valve disease. Repair without ring annuloplasty is a predictor of recurrent MR and need for reoperation. Most first-time reoperations after mitral valve repair result in replacement, for which preservation of the subvalvular apparatus should be attempted as this has been shown to reduce operative mortality and preserve LVEF. Major factors to consider in discussions regarding bioprosthetic vs. mechanical MVR include patient age, life expectancy, comorbidities, and bleeding risk from anticoagulation. Bioprosthetic valves will deteriorate, and the rate of structural valve deterioration and need for reoperation are inversely related to patient age at implantation. Mechanical mitral valves require lifelong anticoagulation (INR goal of 2.5-3.5), and the risk of hemorrhagic stroke is 2-4% per patient per year. The rate of thromboembolic complications (1-3% per patient per year) and the risk of prosthetic valve endocarditis are similar between bioprosthetic and mechanical valves. Although mechanical valves do not structurally deteriorate, they are prone to paravalvular leaks and undergo nonstructural dysfunction (pannus formation). The average time to reoperation after primary MVR is similar between bioprosthetic and mechanical valves (mean 11.5 years), though the durability of a mechanical valve can extend years beyond that of a bioprosthetic valve. The majority of bioprosthetic valves are replaced for structural deterioration and most mechanical valves are replaced for paravalvular leak. The operative mortality of redo MVR is approximately 4.7%. There is no significant difference in operative mortality after redo MVR in patients receiving bioprosthetic vs. mechanical valves (5% vs. 4.4%). Mortality rates have decreased in recent years due to earlier intervention prior to significant LV dysfunction and advances in operative techniques and perioperative care.
Operative steps
- Consider femoral or axillary arterial cannulation and femoral venous cannulation prior to redo sternotomy if RV is adherent to chest wall. (refer to Redo AVR chapter for cannulation algorithm).
- Redo sternotomy is the most common approach for reoperative mitral valve surgery and demands preoperative identification of patent grafts from prior CABG, proximity of heart to posterior sternum, and RV dilatation. A median sternotomy is necessary in the setting of concomitant CABG or AVR. However, a right lateral thoracotomy is an alternative approach in select patients undergoing exclusive mitral valve surgery (tricuspid valve may also be visualized with this approach).
- Myocardial protection is commonly achieved with cardioplegic arrest with antegrade and/or retrograde cold blood cardioplegia. Strategies for myocardial protection will need to be altered in patients with a patent LIMA-LAD from prior CABG. DHCA or ventricular fibrillatory arrest may be feasible in select patients undergoing exclusive mitral valve surgery without significant AI.
- Standard left atriotomy is begun in Waterston’s interatrial groove and extended inferiorly to provide optimal exposure of the mitral valve. A transeptal approach through a right atriotomy is a common alternative in patients with significant adhesions undergoing reoperative mitral valve surgery.
- In patients undergoing MVR after repair, all attempts should be made to preserve native leaflet tissue and associated chordae tendineae during MVR, as disruption of the continuity between the mitral annulus and LV apex has been shown to result in decreased LV function postoperatively. This can be accomplished by imbrication of the leaflet tissue to the annulus.
- Care must be taken when resecting valve sewing rings to avoid removal of excess annular tissue and subsequent disruption of the atrioventricular junction. There are several options for mitral annular reconstruction, including bovine vs. autologous pericardial patch reconstruction or suture placement across the atrioventricular junction to restore a fibrous mitral annulus.
- In patients presenting with a paravalvular leak after MVR, consider percutaneous closure devices or open repair with pledgeted reinforcing sutures or a bovine pericardial patch prior to excision of a competent valve (though most often these patients require redo MVR). Read the prior operative report carefully. These types of minimally invasive options may be ideal for patients who had a very difficult initial operation with annular reconstruction.
- Determining valve competency with saline test and intraoperative TEE following repair is crucial in identifying need for immediate revision, as residual MR (> 1+) at the completion of surgery is a risk factor for recurrence of moderate/severe MR and need for reoperative mitral valve surgery, and cumulative risk of mortality increases with each reoperation.
Potential questions/alternative scenarios
“The patient requires high-dose pressors as they are weaned from CPB. This pressor requirement persists into postoperative day 1 and a TTE shows a lateral wall motion abnormality. Discuss the complication.”
The distance between the posterolateral mitral annulus and the circumflex artery is 2-4 mm. Patients are at risk for postoperative MI if sutures are placed too wide or deep around the posterolateral annulus during MVR or ring annuloplasty.
“The patient is unable to be weaned from CPB without external V-pacing. The monitor shows complete heart block. Discuss the complication.”
The AV node is deep to the posteromedial commissure. Care must be taken to avoid placing sutures too deep around the annulus during MVR or ring annuloplasty.
“Discuss the risks, management, and prevention of prosthetic valve endocarditis (PVE).”
Risk of infection is greatest during the first three postoperative months and decreases thereafter to < 1% per patient per year after the first postoperative year. Early PVE (within the first 2 mos) is often caused by virulent Staphylococcus infections and has a higher mortality than late PVE, often the result of Streptococcus infections. Infection is localized to the sewing ring of mechanical valves, resulting in abscess formation and dehiscence, while infection of bioprosthetic valves occurs on the leaflets and leads to vegetations and leaflet perforation. Indications for and timing of surgery should be individualized and based on response to antibiotics and hemodynamic stability (refer to Endocarditis chapter). Despite improved outcomes after surgery, PVE continues to carry a high mortality rate, and in patients with prosthetic heart valves, the AHA currently recommends prophylaxis with amoxicillin or cephalexin prior to dental procedures, invasive procedures of the respiratory tract involving biopsy, or excision of infected soft tissues.
“The patient agrees to undergo bioprosthetic MVR. She asks if a third operation will be likely.”
In patients receiving bioprosthetic valve replacements, the freedom from reoperation at 15 years is 80%. Bioprosthetic valves in the mitral position are exposed to increased hemodynamic stress during systole compared to bioprosthetic valves in the aortic position and undergo deterioration at a higher rate. Currently, younger patients are receiving bioprosthetic valves due to improvements in valve design and durability and options for transcatheter valve-in-valve implantation.
Pearls/pitfalls
- Considerations in reoperative surgery include alternative strategies for cannulation, surgical approach to the mitral valve, and myocardial protection.
- Mitral valve repair at primary surgery and at reoperation is associated with lower mortality compared to MVR and should be attempted if possible (this requires a high comfort level with redo repair strategies – it is never wrong to replace especially during a redo).
- Choice of bioprosthetic vs. mechanical MVR should be based on individualized risk of reoperation vs. anticoagulation.
- MVR with leaflet/chordal sparing is associated with improved outcomes but do not compromise your outflow.
- The mitral annulus is near the circumflex artery and AV node.
Suggested readings
- Acquired disease of the mitral valve. Sabiston and Spencer – Surgery of the Chest, 8th edition. 1207-1240.
- Reoperative valve surgery. Cohn L (ed). Cardiac Surgery in the Adult. 3rd edition. 1159-1174.
- Nardi et al. Survival and durability of mitral valve repair surgery for degenerative mitral valve disease. J Card Surg. 2011 Jul;26(4):360-6.
- Suri RM et al. Recurrent mitral regurgitation after repair: should the mitral valve be re-repaired? J Thorac Cardiovasc Surg. 2006 Dec;132(6):1390-7.
- Potter et al. Risk of repeat mitral valve replacement for failed mitral valve prostheses. Ann Thorac Surg. 2004 Jul;78(1):67-72.
